This invention relates generally to hydrostatic transmissions.
Hydrostatic transmissions (“HSTs”), including integrated hydrostatic transmissions (“IHTs”), are well known in the art and are more fully described in, among others, U.S. Pat. No. 5,314,387, which is incorporated herein by reference in its entirety. Generally, an HST includes a center section or the like on which is mounted a hydraulic pump and a hydraulic motor. The hydraulic pump and the hydraulic motor each carry a plurality of reciprocating pistons that are in fluid communication through porting formed in the center section. As the hydraulic pump rotates, the pump pistons move axially as they bear against an adjustable swash plate where the degree of axial movement depends upon the angular orientation of the swash plate. Axial movement of the pump pistons forces a hydraulic fluid through the porting, which forces the motor pistons against a thrust bearing to thereby rotate the hydraulic motor. As the hydraulic motor rotates, hydraulic fluid is returned to the hydraulic pump through the porting. In this manner, the rotation of the hydraulic pump is translated to the hydraulic motor and the rotation of the hydraulic motor may be used to drive one or more axles of a riding lawn mower, small tractor, or the like.
In the art, it is also known to provide an HST for use in connection with a snow thrower. For example, U.S. Pat. No. 6,131,316 to Yoshina describes a snow thrower machine having an axle driving unit in the form of an HIT. The described IHT includes a housing, consisting of a front housing section and a rear housing section, that supports an axle. Disposed in the housing are a hydraulic pump, which receives power from an engine, a hydraulic motor, which is driven by pressurized oil received from the hydraulic pump and a center section, having a pump mounting surface parallel to a joint surface between the front housing section and the rear housing section. The axle is supported by the front housing below the hydraulic pump.
While these known IHTs work for their intended purpose, they do suffer various disadvantages. By way of example, mounting known IHTs to a vehicle frame is relatively costly and time consuming. This is particularly true since the non-removeable nature of the axle shaft requires the vehicle frame to have cut-out portions in which the axle shaft may be accommodated. This requires the use of additional hardware to then support the axle shaft within the cut-out portions. Still further, vehicle manufacturers are limited in selecting axle shaft sizes to meet specific operation demands for a vehicle.